Boom Lowering Fuel-Cut Control in Hydraulic Machine Drives
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Solution Overview
Problem
Existing drive systems for construction machines, such as hydraulic excavators and cranes, can improve fuel consumption during energy regeneration at turning deceleration and boom lowering, but there is a need for further enhancement to minimize engine rotation speed fluctuations and ensure continuous operation.
Innovation Solution
A drive system with a controller that adjusts engine fuel injection to maintain a preset rotation speed by cutting fuel supply during energy regeneration at specific conditions, such as when the boom operation lever exceeds a threshold, and resumes fuel supply when the condition is met or the engine speed drops below a certain threshold, thereby optimizing fuel consumption and maintaining stable engine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If fuel supply is cut during energy regeneration to improve fuel consumption, then fuel efficiency is improved, but engine rotation speed may stall significantly or the engine may stop
Solution Approach 1:
The controller continuously monitors the operating amount of the boom operation lever and the actual engine rotation speed, using this feedback to determine when to cut or resume fuel supply. This feedback mechanism ensures that fuel is only cut when the system can tolerate the temporary speed drop, maintaining reliability while improving fuel efficiency.
Solution Approach 2:
The system determines the cutting condition in advance by monitoring the boom operation lever operating amount before actually cutting fuel. By predicting when energy regeneration will occur and preparing the fuel cut condition beforehand, the system can safely cut fuel without causing engine stall, resolving the contradiction between fuel efficiency and reliability.
2Stability of the object's composition
If fuel injection is performed to keep engine rotation speed at setting speed during energy regeneration, then engine speed stability is maintained, but fuel consumption is increased
Solution Approach 1:
Instead of continuously injecting fuel to maintain exact setting speed, the system applies partial fuel cutting during energy regeneration when the boom operation lever operating amount indicates regeneration conditions. This partial action approach accepts temporary speed fluctuations in exchange for significant fuel savings, resolving the contradiction between speed stability and fuel consumption.
3Use of energy by moving object
If fuel supply is cut without determining load conditions, then fuel consumption is improved, but the engine may stop due to insufficient load assessment
Solution Approach 1:
The system performs preliminary assessment of load conditions by monitoring the boom operation lever operating amount before cutting fuel. This advance determination ensures that fuel is only cut when the load conditions are suitable, preventing engine stoppage while maximizing fuel efficiency during appropriate regeneration scenarios.
Solution Approach 2:
The boom operation lever operating amount serves as an intermediary indicator that reflects both the operator's intent and the current load conditions. By using this intermediary parameter, the controller can indirectly assess whether the engine can tolerate fuel cutting without directly measuring complex load parameters, thereby improving fuel consumption while maintaining reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach further improves fuel consumption efficiency and minimizes engine rotation speed fluctuations, ensuring continuous operation by precisely determining the cutting and resumption conditions based on lever operation, reducing the need for a regenerative motor and simplifying the system structure.
Implementation Method 1
the pump being driven by pressurized oil discharged from the boom cylinder at boom lowering
Implementation Method 2
energy is regenerated as motive power owing to the pump being driven by pressurized oil discharged from the boom cylinder
Data Source
AI summary
A drive system of a construction machine includes: a controller that controls a fuel injection valve, so an actual rotation speed of an engine is adjusted to a setting rotation speed; a hydraulic circuit including a boom cylinder supplied with hydraulic oil from a pump driven by the engine, configured so energy is regenerated as motive power owing to the pump being driven by pressurized oil discharged from the boom cylinder at boom lowering; and a boom operation device including a boom operation lever. At boom lowering, the controller cuts a fuel supply to the engine when a cutting condition is satisfied, which is defined to include that an operating amount of the lever is less than or equal to a first threshold, and resumes the fuel supply when the cutting condition stops being satisfied or when the actual rotation speed of the engine becomes less than a second threshold.